Process of recovering precious metals from mattes containing them.



UNITED STATES FFTQEQ FRANKLIN R. CARPENTER, OF DENVER, COLORADO, ASSIGNOR OF ONE- HALF TO JOSEPH H. BERRY, OF DETROlT, MICHIGAN.

PROCESS OF RECOVERING PRECIOUS METALS FROM MATTES CONTAINING THEM.

SPECIFICATION forming part of Letters Patent 'No. 718,089, dated January 13, 1903.

Application filed Septemher lii, 1,902. herial No. 128,324- (No SDRGlIT'Ons.l

To all whom ii; may concern.-

Be it known that I, FRANKLIN R. CARPEN- TER, a citizen of the United States, residing at Denver, in the county of Arapahoe and State of Colorado, have invented certain new and useful Improvementsin Processes of Recovering Precious Metals from Mattes- Containing Them, of which the following is aspecification.

My invention relates to a process of recovering precious metals from mattes containing them, and especially from mattes produced by smelting dry ores.

The treatment of mattes containing precious metals with baths of molten lead is for the purpose of dissolving and concentrating the precious metals in the lead and is well known; but certain difficulties have been found to exist in practicing the process.

It has been found in practice that when matte is brought in contact with a moltenlead bath certain reactions take place between the lead and some'of the metallic snlfids contained in the matte, resulting in a reduction of the sulfid of the metal or metals and the formation of lead sulfid. The presence of the lead sulfid thus produced in the molten-lead bath prevents its absorbing silver to a variable degree, depending on the quantity of sulfid present, thereby preventing efficient concentration and, what is more serious, a loss of silver in the matte. Moreover, lead sulfid is freely soluble in matte and when formed as above described tends to combine with and be carried away with the discharged matte, thereby causing a loss of lead. Moreover, it has been found that when the bath of metallic lead is contaminated with lead sulfid it absorbs copper from the matte, which makes the subsequent treatment of the lead bullion more difficult. Attempts have been made to overcome these difficulties, as by attempting to reduce the lead sulfid contained in the bath of metallic lead; but this is not found to be efficient. It obviously will not prevent the carrying 0d of lead by the matte, nor will it more than partially removethe other difficulties.

It is the object of my invention to produce a process by which the precious metals may be effectively recovered from matte containing them by means of a bath of metallic lead without substantial loss; and to this end my invention consists in causing the matte to be intimately mixed with metallic iron while it is being subjected to the bath of molten lead.

In practicing my invention it will generally be found convenient and preferable to form the mixture of metallic iron and matte by dissolving the former in the latter while in a moltencondition. The addition may consist of wrought or cast iron or steel scrap, which it has been found will readily dissolve in the molten matte, and the presence or absence of iron sulfid (an ordinary constituent of matte) in no way affects this operation. The quantity of metal to be added may be readily determined by experiment, especially when op erating on mattes of substantially constant composition; but the quantity to be used will vary according to the composition of the matte. The quantity of iron to be used may also be determined with safety as that theoretically snflicient to effect the reduction of the metallic sulfids contained in the matte which are capable of being reduced by metallic iron at the temperature to be employed. The solution of the iron in the matte may be effected in any suitable or desired place. For instance, the iron may be dissolved in the molten matte in the forehearth of a cupola or other form ace'in which the matte may have been produced or in any furnace in which the matte may have been melted or in a ladle or other vessel used for conveying the molten matte to the lead-bath. It will be found that the iron dissolved in the matte does not segregate on cooling. The matte containing metallic iron is then subjected to the action of a bath of metallic lead in any suitable or desired way, and after the usual treatment therewith it will be found to be completely freed from the precionsmetals which have become dissolved in the molten lead and no appreciable quantity of lead has been absorbed by the matte.

From the preceding description the advantages of my process will be apparent. In-

stead of attempting to reduce the lead sulfid already formed in the leadbath I cause the iron to be present at the point where the lead of metallic iron.

mixture might be formed by reducing the iron sulfid either before or during the time it is subjected to the lead-bath. If the matte does not contain sufficient iron sulfid, soluble and reducible compounds of iron may be added instead of metallic iron and the mixture treated in the same way as mattes containing iron sulfid.

The reduction of an iron compound contained in the matte is not specifically claimed herein, as the same forms the subject of a separate application, Serial No. 28,343, filed August 28, 1900.

What I claim herein, and desire to secure by Letters Patent, is

l. The process of separating precious metals from matte containing them, which consists in causing an intimate mixture of the matte with metallic iron and subjecting the mixture to a bath of molten metallic lead, substantially as described.

2. The process of separating precious metals from matte containing them, which consists in dissolving metallic iron in molten matte, and then subjecting the mixture to a bath of molten lead, substantially as described.

In testimony Whereof I have hereunto subscribed my name.

FRANKLIN R. CARPENTER.

Witnesses:

FRED SMITH, GEORGE VICKERS. 

